Ну, например, можно так:

[code]
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Memo1: TMemo;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var
i:integer;
begin
for i:=1 to 1000 do
Memo1.Lines.Add(IntToStr(i));
end;

end.
[/code]

Можно, кстати, и другим способом... Все зависит от того, что, за программа.

Я немного опоздал
-----------------------------
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Memo1: TMemo;
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
i : Integer;
begin

for i := 1 to 1000 do
begin
Memo1.Lines.Add(IntToStr(i));
end;
end;
end.